User Guide

Creates or updates an alarm and associates it with the specified metric or metric math expression.

When this operation creates an alarm, the alarm state is immediately set to INSUFFICIENT_DATA . The alarm is then evaluated and its state is set appropriately. Any actions associated with the new state are then executed.

When you update an existing alarm, its state is left unchanged, but the update completely overwrites the previous configuration of the alarm.

If you are an IAM user, you must have Amazon EC2 permissions for some alarm operations:

iam:CreateServiceLinkedRole for all alarms with EC2 actions

ec2:DescribeInstanceStatus and ec2:DescribeInstances for all alarms on EC2 instance status metrics

ec2:StopInstances for alarms with stop actions

ec2:TerminateInstances for alarms with terminate actions

ec2:DescribeInstanceRecoveryAttribute and ec2:RecoverInstances for alarms with recover actions

If you have read/write permissions for Amazon CloudWatch but not for Amazon EC2, you can still create an alarm, but the stop or terminate actions are not performed. However, if you are later granted the required permissions, the alarm actions that you created earlier are performed.

If you are using an IAM role (for example, an EC2 instance profile), you cannot stop or terminate the instance using alarm actions. However, you can still see the alarm state and perform any other actions such as Amazon SNS notifications or Auto Scaling policies.

If you are using temporary security credentials granted using AWS STS, you cannot stop or terminate an EC2 instance using alarm actions.

The first time you create an alarm in the AWS Management Console, the CLI, or by using the PutMetricAlarm API, CloudWatch creates the necessary service-linked role for you. The service-linked role is called AWSServiceRoleForCloudWatchEvents . For more information, see AWS service-linked role .

If you are creating an alarm based on a math expression, you cannot specify this parameter, or any of the Dimensions , Period , Namespace , Statistic , or ExtendedStatistic parameters. Instead, you specify all this information in the Metrics array.

--namespace (string)

The namespace for the metric associated specified in MetricName .

--statistic (string)

The statistic for the metric specified in MetricName , other than percentile. For percentile statistics, use ExtendedStatistic . When you call PutMetricAlarm and specify a MetricName , you must specify either Statistic or ExtendedStatistic, but not both.

Possible values:

SampleCount

Average

Sum

Minimum

Maximum

--extended-statistic (string)

The percentile statistic for the metric specified in MetricName . Specify a value between p0.0 and p100. When you call PutMetricAlarm and specify a MetricName , you must specify either Statistic or ExtendedStatistic, but not both.

--dimensions (list)

The dimensions for the metric specified in MetricName .

Shorthand Syntax:

Name=string,Value=string ...

JSON Syntax:

[
{
"Name": "string",
"Value": "string"
}
...
]

--period (integer)

The length, in seconds, used each time the metric specified in MetricName is evaluated. Valid values are 10, 30, and any multiple of 60.

Be sure to specify 10 or 30 only for metrics that are stored by a PutMetricData call with a StorageResolution of 1. If you specify a period of 10 or 30 for a metric that does not have sub-minute resolution, the alarm still attempts to gather data at the period rate that you specify. In this case, it does not receive data for the attempts that do not correspond to a one-minute data resolution, and the alarm may often lapse into INSUFFICENT_DATA status. Specifying 10 or 30 also sets this alarm as a high-resolution alarm, which has a higher charge than other alarms. For more information about pricing, see Amazon CloudWatch Pricing .

An alarm's total current evaluation period can be no longer than one day, so Period multiplied by EvaluationPeriods cannot be more than 86,400 seconds.

--unit (string)

The unit of measure for the statistic. For example, the units for the Amazon EC2 NetworkIn metric are Bytes because NetworkIn tracks the number of bytes that an instance receives on all network interfaces. You can also specify a unit when you create a custom metric. Units help provide conceptual meaning to your data. Metric data points that specify a unit of measure, such as Percent, are aggregated separately.

If you specify a unit, you must use a unit that is appropriate for the metric. Otherwise, the CloudWatch alarm can get stuck in the INSUFFICIENTDATA state.

Possible values:

Seconds

Microseconds

Milliseconds

Bytes

Kilobytes

Megabytes

Gigabytes

Terabytes

Bits

Kilobits

Megabits

Gigabits

Terabits

Percent

Count

Bytes/Second

Kilobytes/Second

Megabytes/Second

Gigabytes/Second

Terabytes/Second

Bits/Second

Kilobits/Second

Megabits/Second

Gigabits/Second

Terabits/Second

Count/Second

None

--evaluation-periods (integer)

The number of periods over which data is compared to the specified threshold. If you are setting an alarm that requires that a number of consecutive data points be breaching to trigger the alarm, this value specifies that number. If you are setting an "M out of N" alarm, this value is the N.

An alarm's total current evaluation period can be no longer than one day, so this number multiplied by Period cannot be more than 86,400 seconds.

--datapoints-to-alarm (integer)

The number of datapoints that must be breaching to trigger the alarm. This is used only if you are setting an "M out of N" alarm. In that case, this value is the M. For more information, see Evaluating an Alarm in the Amazon CloudWatch User Guide .

--threshold (double)

The value against which the specified statistic is compared.

--comparison-operator (string)

The arithmetic operation to use when comparing the specified statistic and threshold. The specified statistic value is used as the first operand.

Used only for alarms based on percentiles. If you specify ignore , the alarm state does not change during periods with too few data points to be statistically significant. If you specify evaluate or omit this parameter, the alarm is always evaluated and possibly changes state no matter how many data points are available. For more information, see Percentile-Based CloudWatch Alarms and Low Data Samples .

Valid Values: evaluate|ignore

--metrics (list)

An array of MetricDataQuery structures that enable you to create an alarm based on the result of a metric math expression. Each item in the Metrics array either retrieves a metric or performs a math expression.

If you use the Metrics parameter, you cannot include the MetricName , Dimensions , Period , Namespace , Statistic , or ExtendedStatistic parameters of PutMetricAlarm in the same operation. Instead, you retrieve the metrics you are using in your math expression as part of the Metrics array.

--cli-input-json (string)
Performs service operation based on the JSON string provided. The JSON string follows the format provided by --generate-cli-skeleton. If other arguments are provided on the command line, the CLI values will override the JSON-provided values. It is not possible to pass arbitrary binary values using a JSON-provided value as the string will be taken literally.

--generate-cli-skeleton (string)
Prints a JSON skeleton to standard output without sending an API request. If provided with no value or the value input, prints a sample input JSON that can be used as an argument for --cli-input-json. If provided with the value output, it validates the command inputs and returns a sample output JSON for that command.

This command returns to the prompt if successful. If an alarm with the same name already exists, it will be overwritten by the new alarm.

To specify multiple dimensions

The following example illustrates how to specify multiple dimensions. Each dimension is specified as a Name/Value pair, with a comma between the name and the value. Multiple dimensions are separated by a space: